Typically, an inkjet cartridge comprises an outer housing within which an ink containment system or ink reservoir is disposed in fluid communication with an inkjet printhead. A mechanism linked to the ink reservoir generates a negative pressure or backpressure that is maintained within a sufficient range to prevent ink from leaking from the printhead, but also allow injection of ink for printing.
Controlling the internal pressure within the ink reservoir has been the subject patents for more that twenty years. Earlier now expired patents including U.S. Pat. Nos. 4,422,084 (the '084 patent); 4,509,062; and, 4,500,895 (the '895 patent) disclose a variety of mechanisms used to generate and control a negative pressure in an ink reservoir. The '084 and '895 patents disclose pouch, bag or bladder-like configurations that rely on the elasticity of the materials composing the reservoirs to generate the negative pressure. The '084 patent also discloses using a biasing means disposed within the ink reservoir to urge walls of the reservoir apart from one another, or moving one wall apart from another fixed wall.
To that end, the '084 patent discloses an ink containment system that incorporates a single flexible membrane secured within a cartridge housing and forming an ink reservoir with the walls of the cartridge. A spring is not disposed within the reservoir, but outside the reservoir and biases the flexible membrane away from the cartridge walls to generate a negative pressure in the ink reservoir. A similar such design is disclosed in the '062 patent.
In later issued patents there is disclosed cartridges that have two moveable sidewalls that form the ink reservoir and a biasing means disposed between the sidewalls to create negative pressure. For example in U.S. Pat. Nos. 5,325,119; 5,440,333; 5,737,002; 5,767,882; and, 6,053,607, there is disclosed inkjet cartridges having two flexible sidewalls secured to an internal frame structure to form an ink reservoir. Each of the moveable sidewalls comprises a plate member covered by a flexible membrane. The peripheral edge of each membrane is secured to an internal frame structure attached to the walls of the cartridge housing thereby forming the ink reservoir or ink bag. A pressure regulator is disposed within the ink bag and includes two side plates and a spring disposed between the plates biasing the two plates apart from one another and toward the membranes. The spring disclosed in most of these patents is a bow or leaf spring; however, the '119 patent shows an embodiment with a helical spring. As ink is ejected from the cartridge the reservoir collapses including both sidewalls moving toward one another. The spring biases the sidewalls apart to generate the negative pressure.
A drawback in this design is that the plates, especially metal plates, the flexible membrane may have a tendency to tear at the points or lines of engagement of the membrane against edges of the plate. The '333 patent offers a way of preventing the tearing the membranes by securing a protective cover layer between the plate and the membrane. The membrane is heat bonded to the cover layer in a centrally located rectangular area of the side membrane, cover layer and plate. However, such a system adds additional steps to the manufacturing process that may be avoided using different materials that may be more compatible with one another. The '333 patent offers an alternative embodiment in which the membrane is bonded directly to the plate in the absence of the cover layer, which embodiment may still expose the membrane to the edges of the plates; however, this embodiment is not linked to the bonding means as claimed.
In these above cited patents, and other patents owned by the same assignee, Hewlett Packard, methods and materials are disclosed for manufacturing inkjet cartridges For example, in the '002 patent there is disclosed an inkjet cartridge having an ink bag design similar to that disclosed in the '333 patent. The '002 patent is directed to materials used to fabricate components of the inkjet cartridge. More specifically, the inkjet cartridge includes an external frame member having an internal frame member mounted thereon for attachment of the ink bag. The external frame member is composed of a first plastic material and the internal frame member is composed of a second plastic material. An ink bag in the cartridge includes two membranes each of which is composed of a third plastic material. The second plastic material and third plastic material are compatible with another so the membranes may be bonded to the internal frame member to form the ink bag.
In addition, the external and internal frame members are fabricated using what is known as a “two-shot” molding process. The external frame member is formed using an injection molding process, which is the “first shot”, which is then inserted into a second mold for where the second plastic material is molded to the external frame member to form the internal frame member.
In the above referenced patents assigned to Hewlett Packard, and the U.S. Pat. No. 6,206,515 (the '515 patent), a printhead is mounted onto a snout portion of the cartridge. The snout is incorporated as an integral component of the external frame member as compared to fabricating the snout as a component separate from the external frame and mounting the snout to the frame member.
In U.S. Pat. No. 5,450,112 (the '112 patent) there is disclosed an ink bag for an inkjet cartridge that includes two flexible membranes bonded to an internal frame member to form the ink bag. Requirements for materials composing the membrane include flexibility, gas/moisture barrier, chemical resistance, mechanical toughness, heat sealability and cost. A laminate structure is disclosed to apparently meet these requirements. The membranes include a laminate structure including two laminated layers adhered to one another. Each laminated layer includes a carrier layer, a barrier layer affixed on a first surface of the carrier layer and a sealant layer affixed to a second surface of the carrier layer. The barrier layers for each of the laminated layers are affixed one another by an adhesive form the laminated structure. The barrier layer disclosed is an aluminum film on a surface of the carrier layer.
Sidewalls including a flexible membrane and plate members are also disclosed in U.S. Pat. Nos. 6,773,099; 6,830,324 (the '324 patent); 7,004,572; 7,077,514; and, 7,104,640. In each case there is disclosed a single moveable member secured against walls of a cartridge housing forming an ink reservoir. The moveable member includes a preformed flexible membrane for receiving a plate member. A spring is disposed in the ink reservoir between the housing and plate member biasing the moveable member away from the housing wall to create a negative pressure. In other embodiments, the spring is disposed with the cartridge housing between the moveable member and a wall of the cartridge outside of the ink reservoir. As ink is depleted from the ink reservoir, the moveable member collapses along a periphery of the plate. As noted above, the flexible membrane is preformed having a centrally located area on the membrane for receiving the plate, which may create additional steps and costs in the manufacture of the cartridge.
Additional components have been provided to inkjet cartridges, in addition to the above-described mechanism for generating and controlling a constant negative pressure in an ink reservoir. In the '099, '572, '514 and '640 patents, a one-way valve is placed in fluid communication with the ink reservoir. A flexible membrane and plate member open and close openings in the valve in response to changes in pressure within the ink reservoir. If the pressure exceeds a limit, the one-way valve opens to introduce ambient air into the reservoir to decrease the negative pressure so that ink may be effectively ejected from the printhead.
In addition, pressure chambers disposed outside of the ink reservoir have been utilized in lieu of, or in addition to biasing means disposed within the ink reservoir for maintaining a constant negative pressure in an ink reservoir. In U.S. Pat. No. 5,764,259 there is disclosed an inkjet cartridge having negative pressure regulating chamber disposed within the cartridge to maintain a constant negative pressure in the ink reservoir. A bellows-type contracting and expanding wall is attached to a cartridge wall and a regulating plate. The ink reservoir constitutes the remaining interior of the cartridge outside the pressure regulating chamber. In addition, the chamber is in fluid communication with the atmosphere via an aperture in the cartridge wall.
When ink fills the reservoir, the plate and wall constrict in a retracted position. As ink empties from reservoir during printing operations, wall expands against the resistance from the wall creating the negative pressure in the reservoir. When the wall of the pressure regulating chamber reaches a maximum expansion, air is introduced into the chamber in the form of air bubbles through an aperture in the cartridge wall outside the pressure chamber an in the ink reservoir. The negative pressure is maintained within a predetermined range by the capillary force at the aperture.
U.S. Pat. No. 7,033,007 discloses a pump mechanism that presses against the bias of a spring in an ink chamber pressurizes the chamber at a suitable pressure for drawing ink from the chamber. When the chamber is depleted of ink, the pumping mechanism is released and the spring biases the chamber in a direction to draw ink from a reserve ink supply. However, such valves and pumping mechanism increase the complexity, cost and repair of the cartridges.
In published applications U.S. 2005/0157040 A1 and U.S. 2005/0157030 A1 there is disclosed an inkjet cartridge that includes a collapsible reservoir including an annular flexible membrane (bag) secured at each end to plates. One plate is fixed and the other plate slides within a frame having struts as the bag collapses from depletion of ink or expands as it is filled with ink. Negative pressure is created by a spring attached to the moveable plate and the frame outside of the ink reservoir.
A published application, U.S. 2006/0221153 A1, discloses a stress dampening unit disposed between a collapsible ink cartridge and the wall of the cartridge housing. The stress dampening unit includes a flexible cylindrical membrane attached to the flexible membrane of the ink reservoir. A compression spring is disposed within the ink reservoir. In addition, a second compression spring may be disposed in the dampening unit. An orifice in the wall of the cartridge at the dampening unit provides fluid communication between the dampening unit and atmospheric air. As the ink reservoir collapses as a result of an impact, such as may occur if the ink reservoir is dropped or hit against a desk, the dampening unit may minimize the collapse of the ink reservoir. In addition, the dampening unit may be used to control the increase of negative pressure in the ink reservoir.
Systems that utilize springs and flexible membranes are not limited to positioning the spring within the ink reservoir. Some cartridges have mechanisms disposed outside of the ink reservoir, attached to a collapsible wall and pulling on the wall to generate the negative pressure, as compared to systems that have an internally mounted spring, which systems push a moveable wall away from another wall forming the reservoir. A spring mounted external of the ink reservoir is shown U.S. Pat. No. 6,505,924, which discloses cantilevered spring plates mounted externally relative to the ink reservoir. An externally mounted cantilevered spring is also shown in U.S. Pat. No. 6,908,180.
Some cartridges utilize bag-like or bladder-like pouches to form a collapsible reservoir. Examples of such ink reservoirs may be seen in U.S. Pat. Nos. 6,736,497; 6,412,894 (FIG. 5); 6,364,474; and U.S. Publication No. 2006/0098063 A1.
Some systems or devices used to generate negative pressure in an ink reservoir include a porous material such as a sponge or foam core disposed within the cartridge housing. In such cases, the walls of the housing define the ink reservoir which is connected to a printhead, and the absorption of the ink in the sponge acts to generate the negative pressure.
Inkjet cartridges typically incorporate systems, devices or methods for detecting an ink level in a cartridge or ink reservoir. Inkjet cartridges have a minimum level or volume of ink at which the inkjet cartridge may effectively operate. If the volume of ink drops below the minimum level the cartridge risks blank ejections, which may damage the printhead. Prior patents disclose various ink level sensing techniques, including systems employing optical sensing devices, systems that test the electrical conductivity or transparency of the ink to determine an ink level and systems that require visual inspection of components to determine an ink volume remaining in the cartridge.
In those patents disclosing optical sensors, a part is connected to a flexible membrane of a collapsible ink reservoir. The devices are configured so that once the flexible membrane collapses to a predetermined level or position in the ink reservoir the sensor is activated. U.S. Pat. No. 4,342,042 discloses a reflective dot on the membrane and detector including a light emitting diode and photo-transistor. As the reflective dot moves up and down with the change in the ink volume, the photo-transistor detects more or less reflected light.
U.S. Pat. No. 4,604,633 discloses an ink level detecting system that includes light shielding plate connected to a flexible membrane and moves up and down with movement of the membrane as ink is emptied from or injected into the ink reservoir. The shielding plate is disposed between a light emitting element and a light receiving element. The movement of the flexible membrane causes movement of the light shielding plate, which is detected by the light emitting and light receiving elements to indicate a remaining volume of ink in the ink reservoir.
U.S. Pat. No. 5,757,390 discloses an ink level sensing system and method for sensing an ink level that includes the use of a cartridge having two slots, each slot is positioned on opposing walls and aligned to form a light beam path. A light source is mounted on a carriage to generate a light beam, and a detector is mounted on the carriage to generate a signal if it detects light from the light beam. As the cartridge moves on the carriage through the light beam, the ink level may interrupt the beam for detecting a level of remaining ink. The amount of ink is determined by comparing the position of the ink level and the position of the cartridge on the carriage.
U.S. Pat. No. 5,997,121 is directed to an ink level and cartridge detection system that includes two light reflectors formed as an integral part of the cartridge wall. The reflectors are used in conjunction with a two light sources and a photosensor. One light source is a roof mirror that reflects light when the cartridge is positioned on the carriage. The second reflector is a faceted prism used to reflect light to determine an ink level of the cartridge. A similar such ink level and cartridge detection system is disclosed in the U.S. Pat. No. 6,234,603.
The system for detecting an ink supply disclosed in U.S. Pat. No. 5,844,579 is directed to cartridge that has a pump to force ink from a reservoir. An actuator drives the pump. A sensor associated with the pump detects when the actuator is in a position that represents the ink in the reservoir is depleted.
As mentioned above, some ink level detecting systems utilize the electrical conductivity of the ink as component of an ink level sensing system. The sensing system disclosed in U.S. Pat. No. 4,977,413 is directed to an ink remain detector that is disposed in a fluid path from an ink tank to a recording head. The detector includes a pair of electrodes connected to a first alarm and a pair of electrodes connected to a second alarm. Both pairs of electrodes are fixed within an interior of the cartridge; and, conductive plates move responsive to movement of the flexible membrane between the pairs of electrodes to determine a remaining ink volume. Alarms connected to the electrodes sound when the connector plates come in contact with the electrodes.
In U.S. Pat. No. 6,554,382 there is disclosed an ink level sensing system in an inkjet cartridge that includes a first and second resistance probe mounted in respective ports that protrude from a bottom of a cartridge. The ports and probes are in fluid communication with an ink reservoir. When the reservoir and ports are filled with ink, the resistance across the probes is high. When ink is drawn from the reservoir and one or both of the probes, the resistance is low indicating that the ink level is low.
A patent that discloses an ink level sensing device that includes a visual inspection by an operator is U.S. Pat. No. 4,935,751. The '751 patent discloses a rigid plate attached to one side of a collapsible bag. The cartridge has a window on an end of the cartridge housing. As the ink bag collapses, an end of the plate comes into view within the window. The position of the plate relative to the window indicates a remaining ink volume. The window may also include indicia representing a volume measurement of ink.
Still other patents that use a visual indicator incorporate indicial strips outside the cartridge that move responsive to movement of a collapsible reservoir. One such example is found in U.S. Pat. No. 5,359,353. The strip is attached to a flexible ink bag. As the flexible bag deflates with exhaustion of ink, an indicia on the strip moves in or out of view through a window which is on second strip that overlaps the indicia strip. U.S. Pat. No. 6,736,497 discloses an ink level sensing system that uses a flexible strip attached to a collapsible reservoir bag. Portions of the strip extend outside of the cartridge and are covered by panels with a window. As the bag collapses the strip portions move past the window showing indicia indicative of a remaining ink volume.
Some inkjet cartridges incorporate a technology known as “ink drop counting.” A controller is placed in communication with a printhead on the cartridge and counts the number of ink drops that are ejected from the printhead. Generally, the controller includes a database and/or look up table that includes data relative to one or more ink volumes that are associated with an ink drop count to determine a remaining ink volume. Some ink level systems may use ink drop counting in combination with other detection systems to more accurately determine an ink volume. Others may factor in printhead characteristics such as nozzle temperature to determine an ink drop size and volume. Still others may compare the ink drop data taken over multiple ranges to calculate a remaining ink volume.
In U.S. Pat. No. 4,121,222 there is disclosed a drop counter ink replenishing system for an inkjet printer that discloses a main ink tank and a supply ink tank. The system also includes an ink drop counter that counts the ink drops expelled from a printhead. When the ink drop count reaches a predetermined number, a flow control means is actuated and ink from the supply tank is supplied to the main ink tank. Similarly, U.S. Pat. No. 5,068,806 discloses a system that counts ink drops to determine an ink level within an inkjet cartridge. In the '806 patent, the disclosed system is used with disposable cartridges such that when the ink drop count reaches a predetermined number the cartridge is disposed of and replaced.
U.S. Pat. No. 6,151,039 is directed to an inkjet printing system and method of determining an amount of ink in an ink container that incorporates ink drop counting and sensors that detect remaining ink volume and provide an accurate estimate of ink remaining in a cartridge. An information storage device estimates a volume of ink over a first volumetric range using ink drop count data. The device or method also utilizes a sensing circuit that detects an ink level at a predetermined volume. This sensed volume is used to estimate the ink volume over a second volume range that is different than the first range. The sensed volume is combined with count drop data over the second volumetric range to estimate the remaining ink volume.
In U.S. Pat. No. 6,676,237 there is disclosed a method for correcting calculations of ink amount consumed in a cartridge. The method uses ink drop counting to calculate an amount of ink consumed. A sensor/monitor monitors an ink level to generate a signal when the ink levels falls to a predetermined value. The data from this monitoring is used to correct a residual ink count determined by the ink drop count.
A method and apparatus for detecting a remaining ink in an inkjet cartridge using a sensor/detector and ink drop counting is disclosed in U.S. Pat. No. 6,969,137. The cartridge includes a sensor to detect ink level at a predetermined threshold. If ink drop counting calculates that the volume of ink exceeds the predetermined threshold a correction is made by adding the predetermined amount to the amount remaining as determined by the ink drop count.
Ink level sensing systems may factor in characteristics of or events happening at the inkjet printhead. With respect to U.S. Pat. No. 5,414,452 there is disclosed an ink jet cartridge and ink level sensing system that provides a correction in determining the volume of ink remaining in an ink reservoir. More specifically, the system estimates the volume of ink that evaporates over a predetermined time period and then adds that number to the ink drop count. U.S. Pat. No. 6,820,955 discloses an inkjet printing system that controls ink level in a cartridge by factoring the temperature at the printhead.
With respect to U.S. Pat. No. 6,431,673 there is disclosed a method of determining a volume of ink remaining in an ink jet cartridge by associating the drop count with the weight of the ink spelled. Drop weight estimates are made during intervals using temperature and printing frequency data for each interval. U.S. Pat. No. 6,382,764 discloses a printing method and apparatus for ink drop counting that factor in ink drops that are accumulated in a recovery suction operation.
In addition, inkjet cartridges may also be equipped with memory devices that store data relative to an ink drop count, or remaining volume of ink in an ink reservoir. U.S. Pat. No. 5,788,388 is for an inkjet cartridge with ink level detection means. A chip on the cartridge stores ink depletion data. When the ink level reaches a predetermined threshold a sensor sends a signal to the chip which generates an ink depletion signal. The chip can be reset if the cartridge is filled.
Although not directed to an inkjet cartridge, but to an ink reservoir, U.S. Pat. No. 5,365,312 discloses to an ink reservoir that has thereon an electronic memory means that contains data relative to a fill status of the reservoir. In addition, the memory may contain a counter for determining an expiration of the reservoir.
Still other ink level sensing systems may factor in the movement or position of an inkjet cartridge on a carriage to determine an ink volume. For example, U.S. Pat. No. 5,136,309 is directed to a residual ink quantity detecting means that includes a detection device that detects when ink in an ink supply is low and generates a responsive signal. This first signal is received by a signal output means, which generates a second signal when the pulse width is greater than a predetermined pulse width, and generates a signal indicative of low ink. The printer includes electronic circuitry that enables the signal output means to alter the first detection signal during certain printer operations, such as when the cartridge is making a left or right carriage turn, when the detection device may erroneously generate a signal indicative of a low ink supply due to movement of ink in the ink reservoir.